1. Technical Field
The present invention relates generally to mobile-to-private branch exchange (PBX) telecommunications and in particular to delivering calls from an originating mobile switching center (MSC-O) serving a calling mobile subscriber to a called subscriber's land-line unit by dialing an extension within a PBX. Still more particularly, the present invention relates to employing existing message definitions to obtain a temporary local directory number (TLDN) to facilitate call delivery from the MSC-O to the called PBX extension.
2. Description of the Related Art
Private branch exchanges (PBXs), often referred to interchangeably as private, automatic branch exchanges (PABXs), are commonly employed by enterprises including hotels, large businesses, and government offices to provide external communications access to and from individual enterprise employees. A PBX typically includes a private switch, usually on the enterprise's premises, connected to a common group of lines or trunk circuits running from one or more central offices to provide communications service to a number of individual phones. Originally, PBXs required an operator to place any external calls and to connect incoming calls from the public telephone network to a particular PBX extension. Later, connection to outside lines was made automatic in response to dialing "9" or some other digit (often "0" in Europe), resulting in PABXs. Virtually all PBXs in North America are PABXs, where the terms are utilized interchangeably; however operator-assisted PBXs are still employed outside North America.
Within a PBX, calling parties may usually simply dial a three- or four-digit extension to connect to a called party also within the PBX. With the recent explosion of mobile unit usage by enterprise employees, many enterprises wish to extend support for three- or four-digit dialing for their employees' mobile units, a service often referred to as creating a "virtual private network." However, current solutions for allowing a mobile unit to dial an extension on a PBX rely on the PBX supporting direct inward dialing (DID), which provides the ability for a caller outside the PBX to call an internal extension without having to pass through an operator or attendant. The dialed extension digits are prefixed with sufficient digits to create a public switched telephone network (PSTN) translatable number which is utilized to route the call from the serving mobile switching center to the PBX. This technique does not work if the PBX or the PSTN switching center to which the PBX is connected does not support direct inward dialing, which is commonly the case in South America and many developing countries.
It would be desirable, therefore, to provide a mechanism allowing wireless infrastructure to support virtual private network service from a mobile phone when the associated PBX or PSTN switching center to which the PBX is connected does not support direct inward dialing.